The invention relates generally to safety belt retractors, and more particularly to a compact safety belt retractor which is suitable for automotive use.
In many passive or automatic seat belt systems, the seat belt extends from the car door into the location between the front seats. These systems require a longer seat belt than the non-passive systems where the seat belt is not hooked to the vehicle door. The present invention is directed to solving the problem of how to store a long length of seat belt in a coil in a small, compact retractor and still allow the pawls to have locking engagement with the pair of ratchet wheels, which are fixed to the reel shaft. Often the timing of this locking engagement is controlled by an additional plastic, drive ratchet wheel and a plastic drive pawl operated by an inertia mass with engagement of the plastic drive causing a timed actuation of the lock bar pawls into spaces between teeth on the ratchet wheels. This time relationship assures that the pawls do not bounce off the tips of the ratchet wheels. In such retractors, there is a channel or U-shaped retractor frame supporting the reel with the ratchet wheels located inside of the frame. The lock bar is pivotally mounted in the frame. At the time of locking engagement between the ratchet wheels and locking pawls, the load from the belt and reel is transferred from the ratchet wheels to the engaged lock bar pawls and laterally outward across the lock bar ends to the pivot locations where the ends of the lock bar are in metal-to-metal, pivotal contact with the sidewalls of the retractor frame. Because of the transfer of high loads, the pawls or lock bar tips and end portions are quite wide. Thus, substantial portions of the lock bar pawls extend inwardly over the belt coil. When the seat belt is fully wound, a large coil of seat belt extending beyond the diameter defined by the ratchet wheel teeth will engage the wide lock teeth and prevent them from engaging and locking with the ratchet wheel teeth. Therefore, if one merely adds more belt to the usual size of reel, the belt coil will be so large that the coil diameter is larger than the locking ratchet teeth diameter. Then, the locking pawls will be held from displacing into the space between adjacent teeth when the reel is fully wound. Unless provision is made to allow the locking bar and pawls to have their full travel to stop reel rotation when the belt is fully wound or almost fully wound, the plastic drive pawl or pick will break or the plastic drive ratchet wheel will break when trying to actuate the locking bar to have its full extent of travel as the reel continues to turn the plastic, drive ratchet wheel.
While the problem can be overcome merely by making the retractor reels and ratchets larger in size, there are many times when the amount of space allotted for the retractor does not accommodate such enlargements of the retractor size. Also, larger size retractors add weight and material cost to the ultimate vehicle when sold. Thus, there is a need for a compact retractor which can have a full spool of webbing of a diameter larger than that defined by the ratchet wheel teeth and still lock the locking pawls and ratchet wheels without risking damage to the drive pawl and drive ratchet wheel.
A general object of the invention is to provide a compact retractor of the foregoing kind.